1. Field of the Invention
The present invention relates to a fluid machine as a compressor to be used for a super charger of a vehicle, for example.
2. Description of Related Art
There has been disclosed in Japanese Patent Application Laid-Open No. 54-54309 (1979) "a silencing apparatus 201 of a positive-displacement fluid machine" as shown in FIG. 1. This silencing apparatus 201 is disposed at a discharge opening 205 of a screw-type compressor 203, and the silencing apparatus 201 is configured by uniting an expansion silencer 207 and a sound absorbing silencer 209.
The expansion silencer 207 is composed of a reflecting plate 211 and a pipe 213 which pierces through the reflecting plate 211. The sound absorbing silencer 209 is constituted so that a sound absorbing material 217 is provided to an inner wall of a casing 215.
A pressure pulsation of a discharge gas of the compressor 203 is reduced in the expansion silencer 207 by interference of a pressure component reflected from the reflecting plate 211 and a pressure component passing through the pipe 213, and further a pulsation pressure is reduced by the sound absorbing material 217 of the sound absorbing silencer 209 l so that the noise is silenced.
In addition, there has been disclosed in Japanese Utility Model Application Laid-Open No. 6-80026 (1994) "a compressor 219" as shown in FIG. 2, and in Japanese Utility Model Application Laid-Open No. 5-47373 (1993) "a mechanical supercharger 221" as shown in FIG. 3.
The compressor 219 and mechanical supercharger 221 are, similarly to the fluid machine of FIG. 1, screw-type compressors, and their driving forces are increased by speed increasing gear sets 223 and 255 so that rotors 231, 233, 235 and 237 are rotated synchronously via timing gear sets 227 and 229.
Gases inhaled from intake openings 239 and 241 are compressed between the rotors 231, 233, 235 and 237 and rotor chambers 243 and 245 so as to be discharged from discharge openings 247 and 249.
In the case of the compressor 219, because of necessity when the rotors 231 and 233 are mounted, an intake casing 251 which is provided with the intake opening 239 is formed separately from a main body section 253 provided with the rotor chamber 243. The intake opening 239 is provided so as to be right-angled with an axial direction of the rotors 231 and 233.
In the case of the mechanical supercharger 221, the intake opening 241 is provided so as to be substantially parallel with an axial direction of the rotors 235 and 237. Similarly to the compressor 219, in order to mount the rotors 235 and 237, the intake opening 241 is formed separately from a rotor chamber 245.
As mentioned above, the silencing apparatus 201 shown in FIG. 1 is mounted to an outside of the compressor 203, and it is large-sized so as not to lower an inlet efficiency. In the above-mentioned conventional fluid machines, there arises a serious problem of noises, and thus a large-sized silencer such as the silencing apparatus 201 is used in order not to lower the inlet efficiency. Such a large-sized silencer cannot be mounted internally, so it is mounted externally like the silencing apparatus 201.
In addition, when an equipment for a vehicle, for example, should be compact, a special silencer is used, but such a silencer has a complicated structure and is expensive.
Furthermore, since at the intake opening 241 ends other than discharging opening ends, there also arises noises, it is desirable to provide with silencing means on the intake opening 241 ends. However, depending upon restriction of space in the engine room of the vehicle, it is difficult to provide with the silencing means on the intake opening 241 ends in such a manner that the silencing means would be provided independently from the fluid machine.